Xray Bursters

Neutron Stars

• Neutron stars are often found in pairs (binary) or multiple systems.
• When in binary pairs, a neutron star can have significant mass, typically around 1.4 stellar masses.

X-Ray Bursters

• Definition: X-ray bursters are neutron stars that exhibit sudden eruptions of X-ray radiation.
• Detected via X-ray telescopes, these eruptions are characterized by extremely high brightness—approximately a thousand times brighter than the sun.

Characteristics of X-Ray Eruptions

• The eruptions are brief yet incredibly intense, classified as violent outbursts.
• The intense brightness from Earth may appear as a bright dot in the sky, while the actual emissions of X-rays could potentially disable navigation, GPS, and cellular communication systems.

Cause of X-Ray Eruptions

• Neutron stars have significantly higher gravity due to their mass, which allows them to pull matter from a companion star in a binary system.
• This matter forms an accretion disk around the neutron star:
  • The accretion disk is a rotating disk of hot gas and matter.
  • As matter accumulates, it becomes increasingly hot due to gravitational forces.
  • When temperatures reach critical levels, X-rays are emitted in pulses.

Cyclic Nature of Eruptions

• The process of building up mass and reaching the temperature for X-ray emission happens in cycles:
  • Accretion Phase: Matter is drawn from the companion star, forming an accretion disk.
  • Heating Phase: The disk heats up as more mass accumulates.
  • Eruption Phase: Upon reaching sufficient heat, X-ray eruptions occur.

Similar Processes

• The processes occurring in X-ray bursters share similarities with those in white dwarf novae or supernovae, indicating common mechanisms in stellar evolution. Further exploration of these phenomena may be found in Chapter 12 (not covered here).